The present invention pertains generally to medical devices and methods, and more particularly to a bioprosthetic heart valve device and related methods for surgical implantation of such bioprosthetic device.
Heart valve replacement surgeries have been performed in human beings for many years. Most frequently, these valve replacement procedures are utilized to replace the mitral or aortic valves of patients who suffer from valvular heart disease.
In particular, surgical replacement of the aortic valve has proven to be a successful mode of treatment of patients who are diagnosed with a) obstruction (i.e., stenosis) of the aortic valve or b) leakage (i.e., regurgitation, incompetence or insufficiency) of the aortic valve. In some patients, symptoms of both obstruction and leakage are present, this being known as xe2x80x9cmixed diseasexe2x80x9d or xe2x80x9ccombined lesionsxe2x80x9d. These types of aortic valvular heart disease may be caused by a number of factors, including congenital deformations, infections, degenerative calcification, and certain rheumatological disorders.
Surgical replacement of the aortic valve is typically performed under general anesthesia, with full cardiopulmonary bypass. An incision is made in the aorta adjacent to the heart, and the leaflets of the endogenous aortic valve are removed along with any calcified surrounding tissue, thereby creating an annular opening (i.e. the xe2x80x9caortic annulusxe2x80x9d) at the site previously occupied by the endogenous aortic valve. Thereafter, a prosthetic aortic valve is selected and sutured into the aortic annulus, as a prosthetic replacement for the surgically-removed endogenous valve.
The available types of prosthetic aortic valves have heretofore included mechanical valves as well as valves formed of preserved animal tissue (i.e., xe2x80x9cbioprostheticxe2x80x9d valves). Of the bioprosthetic valves, some (known as xe2x80x9cstentedxe2x80x9d bioprosthetic valves) incorporate a man-made stent or support frame upon which the preserved biological tissue is mounted. Others (known as xe2x80x9cstentlessxe2x80x9d bioprosthetic valves) do not include any man-made stent or support frame, and are formed entirely of preserved biological tissue.
Tissues for use in bioprosthetic heart valves are typically harvested from the hearts of donor animals and such tissues typically contain large amounts of connective tissue proteins (e.g., collagen and elastin). After the desired tissues have been harvested from the donor animals, they undergo a chemical xe2x80x9cfixingxe2x80x9d process wherein the connective tissue proteins within the tissue are exposed to one or more chemical cross linking agents capable of forming chemical cross linkages between amino groups present on the connective tissue protein molecules. The types of chemical cross linking agents useable for this purpose include: formaldehyde, glutaraldehyde, dialdehyde starch, hexamethylene diisocyanate and certain polyepoxy compounds.
Examples of commercially available stented bioprosthetic valves include the Carpentier-Edwards(copyright), PERIMOUNT(trademark) Pericardial Bioprosthesis (Baxter Healthcare Corporation, Edwards CVS Division, Post Office Box 11150, Santa Ana, Calif. 92711-1150) as well as the Carpentier-Edwards(copyright) Porcine Bioprosthesis (Baxter Healthcare Corporation, Edwards CVS Division, Post Office Box 11150, Santa Ana, Calif. 92711-1150).
Examples of commercially available stentless bioprosthetic valves include the Edwards Prima(trademark) Stentless Bioprosthesis (Baxter Edwards A G, Spierstrasse 5, CH-6848 Horw, Switzerland), the Medtronic Freestyle(trademark) Aortic Root Bioprosthesis (Medtronic, Inc. 7000 Central Avenue NE, Minneapolis, Minn. 55432-3576) and the St. Jude Toronto(trademark) SPV Stentless Bioprosthesis (St. Jude Medical, Inc. One Lillehei Plaza, St. Paul, Minn. 55117).
The stentless bioprosthetic valves may offer superior hemodynamic performance when compared to their stented counterparts, due to the absence of flow restrictions which can be created by the presence of a stent and/or sewing ring. Also, the stentless bioprosthetic valves may exhibit better post-implantation durability than the stented bioprosthetic valves, because they provide a more flexible structure which serves to dissipate stress during the cardiac cycle.
At least one of the previously available aortic bioprostheses (i.e., the Medtronic Freestyle(trademark) Aortic Root Bioprosthesis referred to hereabove) has included a segment of the donor animal""s ascending aorta, along with ligated remnants of the donor""s coronary arteries extending outwardly therefrom. However, because the coronary artery remnants included in this bioprosthesis have been ligated prior to fixation, the lumens of these coronary artery segments are substantially collapsed and occluded. As a result, it is typically necessary for the surgeon to trim away a substantial portion of each coronary artery remnant, prior to anastomosis of the patient""s endogenous coronary arteries thereto.
It is desirable to devise a new stentless aortic bioprosthesis which includes coronary artery remnants which have been fixed in an unligated, natural configuration, such that the lumens of such coronary artery remnants remain patent, and the patient""s endogenous coronary arteries may be anastomosed directly thereto.
The present invention is a stentless aortic bioprosthesis having patent coronary artery protuberances, and related methods for surgical implantation of such bioprosthesis.
In accordance with the invention, there is provided a stentless heart valve bioprosthesis formed of fixed biological tissue, comprising a segment of mammalian aorta having an aortic lumen extending longitudinally therethrough, an inflow end, an outflow end, a plurality of aortic valve leaflets disposed within the aortic lumen. The bioprosthesis includes right and left coronary sinuses, a non-coronary sinus which is situated adjacent to and between the coronary sinuses, and right and left coronary artery segments having coronary artery segment lumens extending therethrough. The coronary artery segments extend outwardly from the coronary sinuses, and the segment of mammalian aorta is fixed with the right and left coronary artery segments defining patent lumens therethrough such that some of the blood which enters the lumen of the aortic segment may flow outwardly through the coronary lumens.
Further in accordance with the invention, mandrel members such as short segments of plastic tubing may be inserted into the lumens of the coronary artery segments, prior to tanning of the tissue, to maintain the patency of the lumens of the coronary artery segments. Ligatures may be tied about the coronary artery segments to hold the mandrel members in place during the tanning (i.e., chemical fixation) process. The mandrel members and any accompanying ligatures may then be removed after completion of the tanning process.
Still further in accordance with the invention, there is provided a method of surgical implantation of an aortic bioprosthesis of the foregoing character to effect a xe2x80x9ctotal rootxe2x80x9d aortic valve replacement. Such method generally comprises the steps of:
1. surgically transecting the patient""s right and left coronary arteries at locations which are spaced distances away from the wall of the patient""s ascending aorta;
2. surgically removing a segment of the patient""s ascending aorta, along with at least the leaflets of the endogenous aortic valve;
3. anastomosing the aortic bioprosthesis to the patient""s native tissues such that the aortic bioprosthesis replaces the removed segment of the ascending aorta; and,
4. either, a) anastomosing the patient""s native coronary arteries (or coronary artery bypass grafts) to the coronary segments of the bioprosthesis, at spaced distances from the wall of the aortic segment of the bioprosthesis or b) ligating or otherwise closing the lumens of the coronary segments and attaching the coronary patient""s native coronary arteries (or coronary artery bypass grafts) at other locations as may be desirable in certain patients.
Still further in accordance with the invention, there is provided a method of surgical implantation of an aortic bioprosthesis of the foregoing character to effect replacement of a defective pulmonary valve. Such method generally comprises the steps of:
1. surgically removing the patient""s pulmonary valve along with an adjacent segment of the pulmonary artery;
2. closing (e.g., ligating, embolizing or placing purse string sutures in) the coronary segments of the bioprosthesis to prevent leakage of blood out of the lumens of such coronary segments; and,
3. anastomosing the aortic bioprosthesis to the patient""s native tissues such that the aortic bioprosthesis replaces the removed pulmonary valve and adjacent segment of pulmonary artery.
Still further in accordance with the present invention, there are provided methods of using the aortic bioprosthesis of the foregoing character to effect xe2x80x9cmini-rootxe2x80x9d or xe2x80x9csub-coronaryxe2x80x9d replacement of a malfunctioning aortic valve. Such mini-root and sub-coronary aortic applications of the bioprosthesis are carried out in accordance with known techniques, by selectively cutting away distal portion(s) of the bioprosthesis and using the remaining portion of the bioprosthesis to carry out a mini-root or sub-coronary aortic implantation procedure.
Further aspects and elements of the present invention will become apparent to those skilled in the art, upon reading and understanding of the detailed description which follows, and viewing of the accompanying drawings.